Production of aromatic aldehydes



Patented July 26, 1927.

urrs s'rra irsasss AUGUSTUS E. CRAVEE, 01? CLIFESIDE, NEW JERSEY, ASSIGNOR TO THE BARRETT GQE- PANY, A GORIEORATIQN OF NEW JERSEY.

EEODUGTIQN 0E ARQMATIG ALDEHYDES.

Ne Drawing.

chlorination of the-side chains and the subsequent hydrolysis of the chlorinated products, by oxidation of the side chains by wet oxidation methods, by modifications of Gattermans synthesis through carbon monoxide and hydrochloric acid or hydrocyanic acid and hydrochloric acid. I am aware of U. S. Patent No. 1,284,887, which claims the vapor phase oxidation of side chains by oxides of vanadium. The following description of my process will make clear the improvements of my invention over the previous processes.

I have discovered that metallic oxides diffor very widely in their catalytic action at elevated temperatures on the aliphatic substituents of aromatic hydrocarbons and also on the aromatic nucleus itself. For example, ortho-xylene vapor when mixed with an oxygen-containing gas, air for instance, and this mixture passed over the oxides of va nadium gives phthalic acid anhydride, ortho toluic aldehyde, maleic acids and a measurable amount of the products of complete combustion, i. e., carbon dioxide and water, these products being in the following proportions of 9.61:1.0:1.2:6.03 respectively, which are based on the relative amounts of these products formed in terms of pounds er 100 ounds of ortho-xylene' passed over t e catalyst. The production of phthalaldehyde was nil. But, however, if this same mixture be passed over uranium oxide, a large yield of.

ortho-toluic aldehyde results Without any apreciable acid'production or complete comliustion. Similar results also hold true for molybdenum oxide, although the yield of ortho-toluic aldehydeis relatively somewhat lower. Furthermore, if a hydrocarbon, such as .mesitylene which contains three methyl Application med Stovcmter 18, 1921. serial No. 518,124.

groups, be passed over vanadium oxide a considerable maleic acid production and com- ,plete combustion result with practically no aldehyde or other acid production, while it passed over uranium oxide under practically the same conditions, only the 1:3:5 dimethyi benzaldehyde (l methyl, 3 methyl, 5 aldehyde) results in a measurable yield, with a negllgible production of acid.

Likewise I have found that when a mixture of meta and para-xylenes is passed over molybdenum oxide or uranium oxide, a corresponding mixture of the toluic aldehydes with practically no acid production results, while when vanadium oxide is used as the catalyst, a measurable amount of maleic acid and the corresponding mixture of the toluic acids is produced along with a relatively small aldehydeproduction. Pseudocumene with. uranium oxide, molybdenum oxide and tungstic oxide have been found to give the 1 :2:4 dimethyl benzaldehyde (1- methyl, 2 methyl, 4 aldehyde) with a negligible acid formation, while with vanadium oxide,-the production of phthalic anhydride to that of this aldehyde was in the ratio of 20.4:1 respectively.

Paracymene was found to give similar results with the oxides of the fifth and sixth groups, namely that with uranium oxide, p-toluic aldehyde wasthe principal product with a negligible .p-toluic acid. and maleic acid formation, while with vanadium oxide a considerable production of these acids was obtained with an accompanying relatively small p-toluic aldehyde formation.

I have also found that if chlorinated aromatic hydrocarbons are subjected to catalysis, the same general results hold true. For example, if a mixture of ortho-chlortoluene vapor and air be passed over a vanadium oxide catalyst, ortho-chlorbenzoic acid, o-chlorbenzaldehyde and maleic acid result, along with an accompanying measurable amount of the products of complete combustion, these products being in the proportions of 1.2 2.17 1.0 1.6 respectively, while if tantalum oxide is used as the catalyst in lieu of vanadium oxide, only ortho-chlorbenzaldehyde is obtained and this in a relatively much greater yield.- The production of acid was found to be negligible as were also the products of complete combustion. Hydro- Elli .aliphatic side chain group and even to disrupt the aromatic nuother,

chloric acid was, of course, produced in all cases in almost theoretical conformity with the roducts formed. 7

e wide variation in the catal tic action of vanadium oxide when com ar I with that of the other oxides of the fth sixth groups of the periodic system is likewise very striki 1y exhibited with toluene. For exam le, tdhiene with vanadium oxide g ves benza dehyde, benzoic acid, maleic acid and a measurable amount of complete combustion, the proportions of these-various products being as follows :--1:2,47 1145:1555 res ectively, while I have found that when the oxides'of mol bdenum, uranium, tanglsten, tantalum an chromium are emplo the only product of partial oxidation is zaldehyde, the accompanying formatlon of acid being negligible.

The above comparison of the catalytic ac-' tion of oxides of the fifth and sixth cups on various aromatic hydrocarbons which are typified by a benzene nucleus, in which arematic hydrocarbons aliphatic side chains are substituted, indicates a vast difierence between vanadium oxi of the fifth and sixth cups. It is seen that such oxides as those of molybdenum, uranium, tungsten and tantalum exert their catal zmg influence direction of alde yde formation involving only the aliphatic side chain, an it is to be likewise pointed outthat if a plurality 0t aliphatic side chains are present, end one of the roups undergoes selective oxi ation to the a dehyde, the production of the dior tri-aldehydes being nil. On the other hand, vanadium oxide is characterized by its ability to carry the selective oxidation of the beyond the aldehydic cleus itself, forming partial oxidation products from the latter. For exam le, if there are two aliphatic groups, ort o to each in the same benzene nucleus (e. g. ortho-xylene) the oxidation with vanadium oxide produces an aromatic ortho-dicarboxylic acid (e. g. phthalic acid) rather than stopping at the intermediate production of an aromatic ortho substituted monocarboxylic acid (e. g. ortho-methyl-benzoic acid) while if the aliphatic groups occupy the meta or para positions to each other (e. g. meta or era-xylene) the oxidation, as far as the si e chains are concerned, stops at the corresponding aromatic substituted acids (e. g. meta or para-toluic acid). Of course, some aldehyde is roduced in all'cases with vanadium oxide, at this is relatively quite small when compared with the acid formation. But as stated previously, the catalytic oxidation with vanadium oxide does not sto with the partial or selective oxidation 0 the aliphatic side chains but proceeds, to a very considerable degree, to split e and the other oxides ractically entirely in theopen the benzene ring or nucleus to form 'maleic anhydride.' In cases of three methyl groups attached to the same benzene nucleus, the specific action of vanadium oxides 1s again demonstrated in that its oxidizing action is more vigorous than the other metals of the-fifth and sixth groups. in no aldchydic products are ormed and phthalic acid is produced in large quantity from pseudocumene. Mesitylene likewise gives substantially no aldehydic products, maleic acid" being practically the only product of partial oxidation.

The production of phthalic anhydride from pseudocumene has a theoretical interest in view of the grouping of the three methyl groups, and can be explained by assumin that the three methyl groups are converte into the eorresonding carboxyl groups and that by a simutaneous splitting 0d" of one molecule of carbon dioxide from the 4 position carboxyl group phthalic acid results, which, under the condltions of the catalysis, immediately loses one molecule or water, thereby reverting to the anhydride.

The reduction of maleic acid may arise trom t e formation cit the corresponding tricarboxylic acid which is unstable under the conditions of the experiment and splits 0d three molecules of carbon dioxide, thereby forming; benzene whichis immediately oxidized to maleic acid.

llli

his very obvious from the preceding de- I scription that the oxides of the fifth and slxt groups other than vanadium oxide are practically exclusively aldeh de-itorming catalysts, while vanadium oxide is more of an acid-forming catalyst. It has been found that these aldehyde-forming oxides do not give the same percentage yields, but the important henomenon is that they are essentially a1 eh deforming catalysts whichdiiferentiate t em from vanadium oxide.-

littll In carrying out this invention the hydro- I carbon is vaporized in any convenient way and is mixed in suitable proportions with an oxygen-containing gas. For this purpose air may be used, or pure oxy en, or ozone, or a mixture of any or all of t see, or othergases which contain free oxygen together with a certain amount of blanketin or diluent gases or steam, inorder to faci itate the control of the rapidit or completeness of the oxidation, may be eneficially employed.

It is desirable that the hydrocarbon vapors should be mixed with an amount of oxygencontaining as at least sufficient to satisfy the theoretical requirement for aldehyde formation, as indicated for example in the equation:

The catalysts may be prepared by depositing a salt of the metal or ot or water soluble lltl compound of the metal on a suitable carrier,

such as pumice, asbestos, etc., and igniting the deposited material to the oxide of the metal. I

The previously described mixtureof hydrocarbon vapor and oxy ell-containing as is then passed through tl ie catalyst, WlllCh is preferably introduced into tubes or containers. The reaction is found to take place most satisfactoril at temperatures ranging between 300 an 700 C., which tempera ture .is dependent, however, on the hydrocarbon in question, the speed of the hydrocarbon-gas mixture through the catalyst, namely, the length of time a molecule of the gas is permitted to remain in contact with the catalytic zone, the ratio of hydrocarbon vapor to oxygen-containing gas, and also on the particular catalyst employed.

After the products or reaction have passed out of the reaction zone, the condensable portions of the same arecondensed and separated in the usual manner for the recovery of the aldehyde, while the uncondenscd gases may be permitted to escape. Any unchanged hydrocarbon may be again passed through the reaction zone, such hydrocarbon having been enriched with oxygen-containing gas when necessary before. recirculating it through the reaction zone.

The following examples will serve to further illustrate the manner in which these catalytic processes are carried out and also the relative activities of the various metallic oxides, but it is the intention' not to be limited to these particular examples, as the proportions, temperatures and catalysts can i e varied over wide limits, and although only the homologues of benzene have been mentioned, this invention is intended to cover other substituted aromatic nuclei, such as naphthalene, anthracene, etc., and their halogenated derivatives.

The yields stated below are based on the proportion of aldehydeobtained to the hy-.

drocarbon oxidized.

Example 1. 0rtho-mylene.Amixture of air and ortho-xylene in the pro ortion of 7.3 parts of air to 1.0 art of ort o-xylene by weight is passed t rough a mol bdenum catalyst heated to a temperature 0 600 C. at a speed equivalent to a time of contact of 0.39 second. A yield of o-toluic aldeh do of about 50% is obtained. Theaci-d pro uction is negligible. I

Example 2. Meta and pam-mylene.-A mixture of air and meta and para-xylene vapor in the proportion of 3.24 parts of air to 1.0 part of the meta and para-xylene mixture by weight is passed through a uranium oxide catalyst and the catalyst heated to 450 C. With a time of contact of about 0.30 second a yield of the corresponding mixture of meta and para-toluic aldehydes of approximately 32% is obtained. Practically no toluic acid or other .acid was produced.

Ewample 3. Pseudo owmene.A mixture of air and pseudocumene vapor in the proportion of 8.3 parts of air to 1.0 part of pseudocumene by weight is passed through a tungsten oxide catalyst heated to 550 C. lVith a time of contact of 0.30 second a yield ofdimethyl benzaldehyde (1:2 dimethyl :4 aldehyde) of 35% results. The production ofphthalic acid is practically negligible.

Example 4. Mesitylena-When a mixture of air and mcsit lene vapor, in the proportion of 8.3parts 0% air to 1.0 part uranium oxide catalyst at 350 C. at a speed equivalent to a time of contact of 0.38 second is used, a yield of dimethyl benzaldehyde (1 :3 dimethyl :5 aldehyde) of about 20% is obtained. Practically no phthalic or maleic acid is obtained.

Ewample 5. Pdm-cymevia-A mixture of air and para-cymene vapor in the proportion of 3.5 parts of air to 1.0 part of paracymene is passed through a uranium oxide catalyst at 450 C. at a speed equivalent to a time of contact of 0.33 second. A yield of p-toluic aldeh do of 17% is obtained along with an extreme y small production of paratoluic acid.

Example 6.0rtho -chlortolz wne.A mixture of air and ortho-chlortoluene vapor in the proportion of 6.3 parts of air to 1.0.part of ortho-chlortoluene by weight is passed through a tantalum oxide catalyst at 500 C. at a speed equivalent to a time of contact of about 0.31 second. A yield of o-chlorbenzaldehyde of 53% is obtained with only an extremely small amount of maleic acid and no o-chlorbenzoic acid. a

I claim v 1. The process of producing an aldehyde which comprises passing, in the vapor phase, 1 part pseudocumene and approximately 8.3 parts air by weight into contact with a metallic oxide, other than vanadium oxide, of the fifth and sixth periodic groups, at a temperature ofapproximately 550 C.

2. The process of producing an aldehyde which comprises pass1ng,'in the vapor'phase, pseudocumene and an'oxygen-containing gas into contact with a' metallic oxide, other than vanadium oxide, of the fifth and sixth periinto contact with a metallic oxide, other than vanadium oxide, of the fifth and sixth periodic roups, and maintaining said contact for about 0.3 of a second at a temperature of approximately 550 C. v

In testimony whereof I aflix my signature.

AUGUSTUS E. ORAVER. 

